Function: This core provides a range of services that are essential to the success of the overall program: * In vivo studies of pulmonary and systematic circulation. * Operation of hypo- and hyperbaric chambers. * Coordination of management of animals in large animal hypobaric chambers at Colorado State University in Fort Collins, CO. * Maintenance of breeding colonies for inbred mice. * Preparation and renewal of animal Services. Provided: In vivo studies of pulmonary and systematic circulation: The Animal Core provides a vital bridge linking in vitro studies in isolated organs and vessels and cultured cells to the in vivo setting. This permits the important test of relevance of concepts developed in reduced preparations to intact animals.